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An Improved Method for Preparing Gravimetric Standard Gas Mixtures of Helium-4 in Nitrogen.
MISSING :7 pages
An improved method for preparing gravimetric standard gas mixtures of helium-4 in nitrogen has been developed by the U.S. Bureau of Mines. A single-pan 12-kg analytical balance that has a sensitivity of 3 mg is used to prepare the mixture. The balance will accommodate a cylinder having a volume of approximately 4 l that weighs approximately 5 kg. The method has been improved to a precision of +/-0.04 pct by performing four successive dilutions, by improved handling of gases in the manifold, and by using an improved analytical method to select high-purity gases.
IH; Report of Investigations;
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division